Thanks for the suggestion Rui. I enabled the workflow in my local. In one scenario i enable workflows for all the page types and try to upload a pdf file (Storing in File System). The upload went quite well but when i save the pdf file it took almost 15 min and came up with error "An error occurred when saving data. Please see event log for more details." In event log it is trying to fetch all records from "CMS_AttachmentHistory" table. But as the data is saved here in binary format, it is not able fetch even 1 record with size over 300 MB.
Then i changed the workflow so that workflow not enabled for "CMS.File" type. Now i upload and save the document without any issue.
I came to conclusion like if a doc is in workflow it is always creating a record in "CMS_AttachmentHistory" table. So i changed the workflow to not enable on "CMS.File" type.